Burning of regenerator flue gas



P 1960 J. A. TE NUYL ET AL 2,952,310

BURNING 2F REGENERATOR FLUE GAS Filed Oct. 28, 1955 2 Sheets-Sheefl INVENTORS JOHANNES A. TE NUYL LUDOVICUS J.P.SMULDERS THEIR ATTORNEY Sept. 13, 1960 .1. A. TE NUYL ET AL BURNING OF REGENERATOR FLUEI GAS 2 Sheets-Sheet 2 Filed Oct. 28, 1955 INVENTORS JOHANNES A. TE NUYL LUDOVICUS J. P. SMULDERS BY awn/0M2 FIG. 4

THEIR ATTORNEY nited States Patent 2,952,310 BURNING or REGENERATOR FLUE GAS" Johannes A. Te Nuyl, Delft, and Ludovicus J. P. Smulders, The Hague, Netherlands, assignors to- Shell Development Company, New'York, N.Y., a corporation of Delaware especially flue gas from'the regenerator of acatalytic cracking operation, and toa burner therefor.

In the catalytic crack of hydrocarbon oils the catalyst is continuously regenerated by burning oif carbonaceous matter under controlled temperature conditions and under conditions of essentially complete utilization of the oxygen in the air supplied for the combustion. This operation results in a large quantity of so-call'ed regenerator gas, or regenerator flue gas, at a temperature .between about 500 and 65-0 C.. -This gas is normally discharged to the atmosphere. While. this gas consists chiefly of inert materials such as nitrogen, water vapor and carbon dioxide, it normally contains some carbon monoxide (e.g., 5-10% by volume). and has a combustion value of the order of 150.to 3.00 cal.. per cubic meter.

It has been proposed to recover some of the 'sensible heat of these leans gases to form low pressure steam in a heat economizer and this has been done to a limited extent It has also been proposedto recover the heatof. combustion as well as the sensible heat but this hasbeen difiicult to accomplish in reasonable apparatus and in a practical way. According to one scheme use is made of a catalyst mass which promotes the combustion of the lean gas. This is eflective but requires costly apparatus. According to another scheme this lean gas is fed into a furnace in which combustion is already maintained by means of conventional gas or oil burners so that the regeneration gas is also burnt in the hot atmosphere formed by this combustion. In this latter method the combustion is not concentrated as desired for boilers of the usual type, but takes place in a large volume so that special furnaces of different construction are necessary.

The object of the invention is to provide a method for the burning of lean gases, and more specifically catalytic cracking regenerator gas, whereby the combustion is con centrated in a small space and consequently may be effected efliciently in steam boilers or furnaces of the usual construction. This object, broadly speaking, is at-' tained by supplying the lean gas pre-mixed with combustion air annularly through a conical flame which is maintained by the combustion of a liquid fuel. This is done in such a manner that the gas mixture is rapidly raised to the combustion temperature (800 C. to 1000 C.) and burns together with the liquid fuel in a small space.

A specific burner designed to allow the combustion of catalytic cracking regenerator gas according to the invention is illustrated in Figures 1 to 4 of the accompanying drawings. While the burner illustrated is specifically designed for this operation, it may be modified in certain particulars as will be apparent to those skilled in this art after considering the following description of its operation.

Figure 1 of the drawing is a plan view in section of the burner mounted in the front wall of a conventional boiler. Figures 2, 3, and 4 are elevations in section 2,952,310 Patented Sept. 13, 1960 taken through the planes 2-2, 3-3, and 44, respectively.

Referring to the drawings, 1 is a tube to which liqu d fuel is supplied by line 3 andwhich carries an vatomizing nozzle 2 at its front end. This nozzle may be, for example, a vortex chamber atomizer or any other type of nozzle which atomizes the liquid fuel in the shape of a cone 11. Cone 11 preferably has. a wide angle, e'.g. about The tube 1 is surrounded by a cylinder 4 which is constructed preferably of a heat resisting' mate-. rial. The back end of the cylinder 4 is attached'to and opens into an air chamber '5 provided with an air. inlet duct 13. Within the air chamber and connected to the cylinder 4 is a means for distributing the air and. int.- parting to it a rotating motion. as it enters tube: 4. In the particular apparatus illustrated this. means. consists essentially of a cage provided with. fins which impart to the incoming air the desired rotating motion. An annular slot 6 is provided around the front end of cylinder 4L This slot is bounded on the inside by cylinder 4' and on the outside by the wall of cylinder 7' which latter is fitted to the furnace Wall 10. The cylinder 71 is likewise con structed of or lined with a heat-resistant material.

In front of the air chamber 5 and surrounding in part cylinder 4 is a. gas chamber 8 communicating with the slot 6 and provided with an inletd'uct 15 for the lean. gas to. be burned; The regeneration gas suppliedby duct 15 enters the chamber 8' and then passes through the slot 6 to the combustion zone. In front of gas. chamber 8 and surrounding in part the cylinder 7 is a third. chamber 9 supplied by an air duct 16. The cylinder 7 is provided with a number .of slotted openings 12 providing communication between. the air chamberz9 and the annular slot 6. These openings or slots 12 enter theannul'ar passageway 6 somewhat .ba'ckxof the end of the cylinder '4, asillustrated, and are preferably inclined somewhat in the direction of flow of flue gas through slot 6.

In operation a liquid fuel is supplied by line 3 to the tube 1 and nozzle 2 by which it is sprayed into the combustion zone in the form of the cone 11. Air for the combustion, introduced by duct 13, passes into the outer chamber 5 and then through the distributor 14 wherein it is given a rotatory motion. The swirling air passes forward through the cylinder 4 around tube 1 to the combustion zone. A further quantity of air introduced through duct 16 passes to the forward or front chamber 9 and from there through the slots 12 into the annular passageway 6. Regenerator flue gas introduced through duct 15 passes to the intermediate chamber 8 which is between the gas chambers 5 and 9 and from it through the slot 6. In passing through the slot 6 the regenerator flue gas is pre-mixed with the air required for its combustion and the mixture is forced to pass through the cone 11. When this mixture of gas and air meets the flame formed by the liquid fuel it rapidly reaches the necessary combustion temperature and burns together with the liquid fuel in a single flame in a very short time.

By effecting the combustion of the flue gas in the manner described the size of the flame thus obtained is not much greater than that of the flame which would obtained if only liquid fuel were burnt in the quantity which would produce the same amount of heat. Thus, the invention enables liquid fuel to be substituted by regeneration gas in a boiler or furnace of conventional design intended to produce a given amount of heat with liquid fuel. This allows considerable saving to be made in the cost of fuel without resort to boilers or furnaces of special construction.

With the burner illustrated it is an easy matter to mount a number of such burners on a furnace wall and in such case the chambers 5, 8 and 9 may be enlarged to accommodate several burners. The regenera- 3 tor flue gas, as pointed out, normally is at a fairly high temperature, e.g., between 500 C. and 600 C. With the burner illustrated the heat which this gas imparts to'the walls of the gas chamber is not lost in view of the position of this gas chamber between the two air chambers;

It has been found that the amount of liquid fuel required to cause the combustion of regenerator flue gas is relatively small. An amount of gas can be burned with an amount of liquid fuel, the total combustion value of which is approximately 50% of the combustion value of the gas. This means that only about 0.01 -ton ofliquid fuel is required to burn one ton of regenerator gas.

It has also been found that the described method of burning regenerator flue gas has a favorable effect on the course of combustion of, very heavy fuels such as liquid asphalt.

It will be noted that the burner used according to the invention is one in which a gaseous fuel and a liquid fuel are supplied at the same time with separate streams of combustion air. The burner is preferably mounted in the furnace wall such that the part of the furnace which directly surrounds the combustion zone has no cooled walls such as are formed, for example, by a part ofthe boiler surface. The free flame formation should not, however, be obstructed by the presence of wall sections especially arranged to promote ignition. The front edge of the cylinder 4 and the edge of the cylinder 7 are preferably so positioned that they closely approach the cone of atomized fuel 11 since when the cone passes close to the top edges of these cylinders the most favorable mixing is obtained between the mixture of gas and air and the burning mass formed from the liquid fuel, As illustrated, it is advantageous to direct the mixture of regenerator gas and air in a direction approximately parallel to the central line of the burner.

We claim as our invention:

1. Process for the burning of catalytic cracking regenerator flue gas containing from about 5 to about 10% by volume carbon monoxide and essentially no oxygen and having a combustion value of 150 to 300 calories per cubic meter with a liquid fuel, the amount of liquid fuel being such that its'calorific value is approximately of that of the catalytic cracking regenerator flue gas, which comprises spraying the liquid fuel in the form of a forwardly diverging conical spray, advancing primary combustion air in a rotating stream coaxially to the conical spray and impinging the combustion air upon the conical spray, igniting the primary combustion air and liquid fuel in the conical spray, uniformly premixing catalytic cracking regenerator flue gas with the required amount of air for combustion of the carbon monoxide therein and passing the flue gas-air mixture coaxially in an annular stream into the forward diverging conical spray so as to impinge upon the conical spray forward of the point of ignition of the liquid fuel.

2. The process of claim 1 in which the forward diverging conical spray has-an angle of about degrees.

References Cited in the file of this patent UNITED STATES PATENTS 1,459,295 Smith June 19, 1923 1,958,671 Mathesius May 15, 1934 1,983,927 Bent Dec. 11, 1934 2,020,047 Bost Nov. 5, 1935 2,217,518 Merkt Oct. 8, 1940 2,344,936 Zink Mar. 21, 1944 2,458,542 Urguhart Ian. 11, 1949 2,531,316. Zink' .Nov. 21, 1950 2,753,925 Campbell July 10, 1956 2,813,578 Ferguson Nov. 19, 1957 FOREIGN PATENTS 878,243- France Jan. 14, 1943 

1. PROCESS FOR THE BURNING OF CATALYTIC CRACKING REGENERATOR FLUE GAS CONTAINING FROM ABOUT 5 TO ABOUT 10% BY VOLUME CARBON MONOXIDE AND ESSENTIALLY NO OXYGEN AND HAVING A COMBUSTION VALUE OF 150 TO 300 CALORIES PER CUBIC METER WITH A LIQUID FUEL, THE AMOUNT OF LIQUID FUEL BEING SUCH THAT ITS CALORIFIC VALUE IS APPROXIMATELY 50% OF THEAT OF THE CATALYTIC CRACKING REGENERATOR FLUE GAS, WITH COMPRISES SPRAYING THE LIQUID FUEL IN THE FORM OF A FORWARDLY DIVERGING CONICAL SPRAY, ADVANCING PRIMARY COMBUSTION AIR IN A ROTATING STREAM COAXIALLY TO THE CONICAL SPRAY AND IMPINGING THE COMBUSTION AIR UPON THE CONICAL SPRAY, IGNITING THE PRIMARY COMBUSTION AIR AND LIQUID FUEL IN THE CONICAL SPRAY, UNIFORMLY PREMIXING CATALYTIC CRACKING REGENETOR FLUE GAS WITH THE REQUIRED AMOUNT OF AIR FOR COMBUSTIN OF THE CARBON MONOXIDE THEREIN AND PASSING THE FLUE GAS-AIR MIXTURE COAXIALLY IN AN ANNULAR STREAM INTO THE FORWARD DIVERGING CONICAL SPRAY SO AS TO IMPINGE UPON THE CONICAL SPRAY FORWARD OF THE POINT OF IGINITION OF THE LIQUID FUEL. 